A lead angle adaptive compensation circuit and a brushless direct current motor

Abstract

The application discloses a lead angle self-adaptive compensation circuit and a brushless direct current motor. The lead angle self-adaptive compensation circuit comprises a phase lead circuit module, a switching circuit module, a current sampling circuit module and a three-phase inverter circuit module. The current in the current sampling circuit module is collected, and the collected current is converted and fed back to the switching circuit module. The lead angle voltage is adjusted through the conduction condition of the switching circuit module. The angle difference between the winding current and the back electromotive force is automatically adjusted. The motor winding current waveform is improved. Smooth torque is obtained. When the motor is used in various environments and various loads, the corresponding lead angle voltage is changed with the change of the load. The motor current and the back electromotive force are in phase, and the phase angle is automatically adjusted. The noise appearing in each speed section of the motor is improved, and the efficiency of the motor is improved. The brushless direct current motor comprises the lead angle self-adaptive compensation circuit. Therefore, the motor is in the most optimal efficiency in each speed section.

Description

Technical Field

[0001] This invention relates to the field of DC motor control technology, specifically to a lead angle adaptive compensation circuit and a brushless DC motor. Background Technology

[0002] Brushless DC motors are widely used in various fields due to their high energy efficiency, long lifespan, and superior control performance. Currently, control schemes for brushless DC motors can choose either a slightly more expensive but high-performance vector control scheme, or a low-cost, performance-comparable dedicated chip scheme. Dedicated chip schemes are simple to apply, highly reliable, and can meet the development needs of low-power and most brushless DC motors. These dedicated chips are brushless DC motor controllers that use a 120° rotor pole position detection three-phase sine wave. They can achieve SVM sine wave PWM output and feature an internal clock generator, error amplifier, current-guided phase correction, and protection against overvoltage, overheating, overcurrent, and Hall signal abnormalities. The current-guided phase technology is particularly important, primarily for compensating for the current phase angle, which directly affects motor efficiency. Due to the inductive characteristics of the stator windings, the actual sinusoidal current flowing into the three-phase coils will lag behind the three-phase input voltage by an angle, causing the sinusoidal current to be out of phase with the back electromotive force, thus preventing the output efficiency from being fully utilized. Therefore, different parameter matching is required for different loads during motor commissioning. In the existing design, the advance angle voltage cannot be automatically adjusted, which leads to increased motor noise and a certain reduction in working efficiency when the motor speed and load change. Summary of the Invention

[0003] Therefore, in order to overcome the shortcomings of existing technologies where the lead angle voltage cannot be automatically adjusted, resulting in a certain reduction in motor efficiency and noise when the motor speed and load change, an adaptive lead angle compensation circuit and a brushless DC motor are provided. This can improve motor noise, increase motor efficiency, and enable the motor to be at its optimal efficiency in all speed ranges.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] This invention provides an adaptive compensation circuit for phase lead angle, comprising: a phase lead circuit module, a switching circuit module, a current sampling circuit module, and a three-phase inverter circuit module, wherein:

[0006] The phase lead circuit module is connected to the external power supply and the switching circuit module respectively. It is used to process the input lead angle voltage and keep it within the preset voltage range, and output the lead angle signal corresponding to the voltage to the brushless DC motor through the three-phase inverter circuit module.

[0007] The current sampling circuit module is used to sample the winding current when the brushless DC motor is running and feed it back to the switching circuit module.

[0008] The switching circuit module is connected to an external power supply. It determines its own conduction state by sampling the voltage and current corresponding to the current from the external power supply input voltage and current sampling circuit module. When it is in the conduction state, it adjusts the lead angle voltage so that the phase lead circuit module adjusts the corresponding lead angle.

[0009] The switching circuit module includes: a transistor, a current-limiting resistor, and a variable resistor, wherein:

[0010] The emitter of the transistor is connected to an external power supply, and the base is connected to a current-limiting resistor.

[0011] The variable resistor is connected to the collector of the transistor and the phase lead circuit module respectively, and is used to change its own resistance value and adjust the lead angle voltage when the transistor is turned on.

[0012] In one embodiment, the phase-leading circuit module includes: a first voltage divider resistor and a second voltage divider resistor, a Zener diode, a filter capacitor, and a phase angle processing chip, wherein:

[0013] One end of the first voltage divider resistor is connected to the external power supply, and the other end is connected to one end of the second voltage divider resistor. The other end of the second voltage divider resistor is grounded. The Zener diode is connected in parallel across the two ends of the second voltage divider resistor. The filter capacitor is connected in parallel across the two ends of the Zener diode. One end of the variable resistor is connected to the collector of the transistor, and the other end is connected to one end of the second voltage divider resistor. The phase angle processing chip is connected in parallel across the two ends of the filter capacitor.

[0014] The phase angle processing chip includes: a third voltage divider resistor, a fourth voltage divider resistor, and a comparator. The third voltage divider resistor is connected in parallel across the two ends of the filter capacitor. One end of the fourth voltage divider resistor is connected to one end of the third voltage divider resistor, and the other end is connected to the input terminal of the comparator. The output terminal of the comparator is connected to the three-phase inverter circuit module. The other end of the third voltage divider resistor and the negative voltage terminal of the comparator are both grounded.

[0015] In one embodiment, the input voltage of the external power supply is divided by a first voltage divider resistor and a second voltage divider resistor, and the output voltage is a lead angle voltage.

[0016] When the input voltage of the external power supply is greater than or equal to the first threshold and less than or equal to the second threshold, the motor starts and the motor winding current is at a non-rated speed. If the transistor conduction condition is met in this voltage range, the variable resistor is adjusted to adjust the lead angle voltage, and the phase lead circuit module adjusts the corresponding lead angle. If the transistor conduction condition is not met, the lead angle voltage value remains unchanged.

[0017] In one embodiment, when the voltage input value of the external power supply is greater than the second threshold and less than or equal to the third threshold, the motor starts and the motor winding current is at the rated speed. If the transistor conduction condition is met in this voltage range, the variable resistor is adjusted to adjust the lead angle voltage, and the phase lead circuit module adjusts the corresponding lead angle.

[0018] In one embodiment, the Zener diode's Zener voltage is not greater than the maximum input voltage of the external power supply.

[0019] In one embodiment, the variable resistor is a thermistor with a negative temperature coefficient. When the temperature rises and the output current waveform is distorted during the operation of the DC motor, the thermistor senses the increase in the internal temperature of the motor and the resistance value decreases accordingly.

[0020] In one embodiment, the variable resistor is a variable resistor, and the resistance value of the variable resistor is manually adjusted when the output current waveform is distorted during the operation of the DC motor.

[0021] This invention also provides a brushless DC motor, including the lead angle adaptive compensation circuit of any of the above embodiments.

[0022] The technical solution of this invention has the following advantages:

[0023] 1. The adaptive compensation circuit for the lead angle provided in this embodiment of the invention includes a phase lead circuit module, a switching circuit module, a current sampling circuit module, and a three-phase inverter circuit module. By collecting the current in the current sampling circuit module, the switching circuit module converts the collected current and feeds it back to the switching circuit module. The lead angle voltage is adjusted by the conduction condition of the switching circuit module, thereby automatically adjusting the angle difference between the winding current and the back electromotive force, improving the waveform of the motor winding current, and obtaining smooth torque. When the motor is used in various environments and under various loads, it will change the corresponding lead angle voltage according to the change of load, so that the motor current and the back electromotive force are in phase and the phase angle is automatically adjusted, improving the noise that occurs in each speed range of the motor, improving the efficiency of the motor, and making the motor at its optimal efficiency in each speed range.

[0024] 2. The brushless DC motor provided in this embodiment of the invention includes a lead angle adaptive compensation circuit, which can improve motor noise, increase motor efficiency, and make the motor at its optimal efficiency in each speed range. Attached Figure Description

[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram showing the connection of the functional modules of the adaptive compensation circuit for the lead angle provided in this embodiment of the invention;

[0027] Figure 2 This is a schematic diagram of a specific embodiment of the adaptive compensation circuit for lead angle provided in this invention.

[0028] Figure 3 This is a schematic diagram illustrating the relationship between the external power supply input voltage and duty cycle provided in an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the lead angle voltage and phase relationship provided in an embodiment of the present invention;

[0030] Figure 5 This is a waveform diagram of the winding current at rated speed provided in an embodiment of the present invention;

[0031] Figure 6 All of these are current waveforms at non-rated speeds before compensation, provided in the embodiments of the present invention. Detailed Implementation

[0032] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] Due to the inductive characteristics of the stator windings of a brushless DC motor, the actual sinusoidal current flowing into the three-phase coils will lag behind the three-phase input voltage by an angle. This causes the sinusoidal current to be out of phase with the back electromotive force, resulting in the output efficiency not being fully utilized. In previous designs, the inability to automatically adjust the lead angle voltage led to increased noise and reduced motor efficiency when the motor speed and load changed.

[0035] To address the above problems, this invention provides an adaptive compensation circuit for the lead angle, such as... Figure 1As shown, it includes: a phase lead circuit module, a switching circuit module, a current sampling circuit module, and a three-phase inverter circuit module, wherein:

[0036] The phase lead circuit module is connected to both the external power supply and the switching circuit module. It processes the input lead angle voltage and keeps it within a preset voltage range. The lead angle signal corresponding to the voltage is then output to the brushless DC motor through the three-phase inverter circuit module. The current sampling circuit module samples the winding current of the brushless DC motor during operation and transmits it to the switching circuit module. The switching circuit module is also connected to the external power supply. It determines its conduction state based on the voltage input from the external power supply and the voltage corresponding to the current sampled by the current sampling circuit module. When it is in the conduction state, it adjusts the lead angle voltage, causing the phase lead circuit module to adjust the corresponding lead angle.

[0037] The adaptive compensation circuit for the lead angle provided in this embodiment of the invention will change the corresponding lead angle voltage according to the change of load, so that the phase lead circuit module adjusts the corresponding lead angle angle, so that the motor current and the back electromotive force are in phase and the phase angle is automatically adjusted, thereby improving the noise that occurs in each speed range of the motor, improving the efficiency of the motor, and making the motor in the optimal efficiency range in each speed range.

[0038] In one embodiment, such as Figure 2 As shown, VSP_IN is an analog input voltage chip, used as an external power supply to control the analog voltage of the motor rotation. The output duty cycle is controlled by the input voltage of VSP_IN. The relationship between VSP_IN and the duty cycle is as follows: Figure 3 As shown. In this embodiment of the invention, the range of input analog voltage is defined as 2.1V ≤ VSP_IN ≤ 5.5V. This is only an example and is not intended to be limiting. In actual applications, it should be determined according to the voltage requirements of the motor and the chip specifications.

[0039] like Figure 2 As shown, the switching circuit module in this embodiment includes: a PNP transistor Q1, a current-limiting resistor R2, and a variable resistor R1. The emitter of the transistor is connected to an external power supply, and the base is connected to the current-limiting resistor. The variable resistor R1 is connected to the collector of the transistor and the phase-lead circuit module, respectively, and is used to change its resistance value and adjust the lead angle voltage when the transistor is turned on. In other embodiments, a multiplexer with a voltage comparator can be used instead of the transistor; this is merely an example and not a limitation.

[0040] In one embodiment, the variable resistor is a thermistor with a negative temperature coefficient. When the temperature of the DC motor rises and the output current waveform becomes distorted and the noise increases during operation, the thermistor senses the increase in the internal temperature of the motor, so the resistance decreases, and the voltage at AS increases. This automatically adjusts the distorted current waveform to make the motor operate at its optimal state.

[0041] In another embodiment, a variable resistor is used, which needs to be manually adjusted according to the actual operating conditions. The value of the variable resistor is determined based on the sinusoidal nature of the current. If adjusting the variable resistor results in a high sinusoidal current, optimal efficiency, and no noise, then the value of the variable resistor at this point is the fixed value.

[0042] like Figure 2 As shown, the phase-lead circuit module includes: a first voltage divider resistor RL1 and a second voltage divider resistor RL2, a Zener diode Z1, a filter capacitor C1, and a phase angle processing chip. One end of the first voltage divider resistor RL1 is connected to the output terminal of the analog input voltage chip VSP_IN, and the other end is connected in series with the second voltage divider resistor RL2. The other end of the second voltage divider resistor RL2 is grounded. The Zener diode Z1 is connected in parallel across the second voltage divider resistor RL2. The filter capacitor C1 is connected in parallel across the Zener diode Z1. One end of the variable resistor R1 is connected to the collector of the transistor Q1, and the other end is connected to the Zener diode Z1 and the filter capacitor C1. The phase angle processing chip is connected in parallel across the filter capacitor. It should be noted that the Zener diode's voltage regulation value is not greater than the maximum input voltage of the analog input voltage chip.

[0043] like Figure 2 As shown, the phase angle processing chip includes: a third voltage divider resistor R3, a fourth voltage divider resistor R4, and a comparator U1. The third voltage divider resistor R3 is connected in parallel across the filter capacitor C1. One end of the fourth voltage divider resistor R4 is connected in parallel with the third voltage divider resistor R3, and the other end is connected to the input terminal of the comparator U1. The output terminal of the comparator is connected to the three-phase inverter. The negative voltage terminals of the third voltage divider resistor R3 and the comparator U1 are both grounded. The function of the phase angle processing chip is to convert the input leading angle voltage into a leading angle signal based on its internal voltage-angle correspondence, so that the motor is always in the optimal operating state.

[0044] In this embodiment of the invention, the input voltage of the analog input voltage chip VSP_IN is divided by the first voltage divider resistor RL1 and the second voltage divider resistor RL2, as follows: Figure 2 As shown, the voltage output by AS is the lead angle voltage U. AS The working principle of the adaptive compensation circuit for the lead angle is as follows:

[0045] When the input voltage value of the analog input voltage chip is less than the first threshold, the motor does not start. When the input voltage value of the analog input voltage chip is greater than or equal to the first threshold and less than or equal to the second threshold, the motor starts, and the motor winding current is at a non-rated speed. If the transistor conduction condition is met within this voltage range, the variable resistor is adjusted to adjust the lead angle voltage, and the phase lead circuit module adjusts the corresponding lead angle to make the DC motor current output waveform close to a sine wave. If the transistor conduction condition is not met, the lead angle voltage value remains unchanged. When the input voltage value of the analog input voltage chip is greater than the second threshold and less than or equal to the third threshold, if the transistor conduction condition is met within this voltage range, the variable resistor is adjusted to adjust the lead angle voltage, and the phase lead circuit module adjusts the corresponding lead angle.

[0046] In one specific embodiment, when the VSP_IN input voltage value is < 2.1V, there is no duty cycle output, and the motor will not run if the starting requirements are not met. The motor starts when 2.1V ≤ VSP_IN input voltage value ≤ 2.5V. As the VSP_IN input voltage value increases, the motor speed also increases. At this time, the output voltage of the VSP_IN input voltage after being divided by voltage divider resistors RL1 and RL2 is U. AS Since the VSP_IN input voltage is small, then U AS After voltage division, a smaller output voltage is obtained. AS The voltage is filtered by capacitor C1, divided by resistors R3 and R4, and then fed into comparator U1. The processed voltage U1... AS The voltage signal flows into the three-phase inverter circuit module and is finally applied to the motor windings. Due to the relatively low speed, the motor output torque is small. When the motor is running, the winding current I is detected by the current sampling circuit module. However, due to the inductive characteristics of the stator windings, the actual sinusoidal current flowing into the three-phase coils will lag behind the three-phase input voltage by a certain angle, causing the sinusoidal current to be out of phase with the back electromotive force, thus preventing the output efficiency from being fully utilized. Current I flows through resistor R2 into the base of PNP transistor Q1. At this time, if the base voltage of the transistor is detected as Ub > Ue and Ub > Uc, the transistor will saturate and conduct. As transistor Q1 conducts, U... AS This voltage also increases accordingly, and the increased voltage is simultaneously fed back to the subsequent circuit (i.e., the components included in the circuit after transistor Q1). As U... AS As voltage increases, the lag angle between the motor current and back EMF decreases, resulting in a near-sinusoidal waveform for the motor winding current at non-rated speeds, leading to smoother torque output. Efficiency improves, temperature rise decreases, and synchronization noise is reduced. However, if the transistor base voltage does not meet the conduction condition, then U... AS The voltage remains constant.

[0047] When the input voltage value of VSP_IN is 2.6 ≤ VSP_IN ≤ 5.5V, the voltage U at AS is... ASAfter being divided by voltage dividers RL1 and RL2, the voltage increases. After interference voltage is filtered out by capacitor C1, it passes through voltage dividers R3 and R4 and U1 before being converted by the three-phase inverter and applied to the motor windings. At this time, due to the increased VSP_IN voltage, the duty cycle of the input winding voltage increases, and the motor output torque increases. When the VSP_IN voltage rises to the rated speed, the motor current waveform is a smooth sine wave without distortion. Figure 4 As shown, noise and temperature rise are at their optimal levels at this point. When the VSP_IN voltage increases further, the motor speed increases, the inductive impedance increases, the angle between the current and the back electromotive force increases, and the required lead angle voltage U... AS Increases because the VSP_IN voltage reaches its maximum value, U AS The voltage at the point did not change, but the waveform of the motor winding current was distorted due to inductance, such as... Figure 5 As shown, a larger angle is required between the current and the back electromotive force, resulting in increased motor output power, increased current, noise, and increased internal motor temperature. At this time, the current sampling circuit module collects the current and sends it to the base of the transistor through the current-limiting resistor R2. If the transistor is turned on, the resistor R1 is adjusted to make U... AS As the voltage increases, the current waveform becomes sinusoidal, achieving the purpose of automatically adjusting the lead angle and keeping the motor in the optimal operating state.

[0048] The adaptive lead angle compensation circuit provided by this invention collects the current in the current sampling circuit module and feeds the collected current back to the voltage of the transistor base. By controlling the conduction status of the transistor, the lead angle voltage is improved, thereby automatically adjusting the angle difference between the winding current and the back electromotive force, improving the waveform of the motor winding current, and obtaining smooth torque. When the motor is used in various environments and under various loads, it will change the corresponding lead angle voltage according to the change of load, so that the motor current and the back electromotive force are in phase and automatically adjust the phase angle, improving the noise that occurs in each speed range of the motor, improving the efficiency of the motor, and making the motor operate at its optimal efficiency in each speed range.

[0049] This invention also provides a brushless DC motor, which includes the lead angle adaptive compensation circuit described in any of the above embodiments. Based on the lead angle adaptive compensation circuit, the winding current waveform of the brushless DC motor can be improved, smooth torque can be obtained, motor noise can be reduced, motor efficiency can be increased, and the motor can be in optimal efficiency at all speed ranges.

[0050] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A lead angle adaptive compensation circuit, characterized by, The application relates to a lead angle self-adaptive compensation circuit. The lead angle self-adaptive compensation circuit comprises a phase lead circuit module, a switch circuit module, a current sampling circuit module and a three-phase inverter circuit module, wherein: The phase lead circuit module is connected with an external power supply and the switch circuit module, is used for processing input lead angle voltage to keep the lead angle voltage in a preset voltage range, and outputs the voltage corresponding lead angle signal to a brushless direct current motor through the three-phase inverter circuit module; The current sampling circuit module is used for sampling the winding current of the brushless direct current motor during operation and transmitting the winding current to the switch circuit module; The switch circuit module is connected with the external power supply, determines the conduction state of the switch circuit module according to the voltage input by the external power supply and the voltage corresponding to the current collected by the current sampling circuit module, adjusts the lead angle voltage when the switch circuit module is in the conduction state, and adjusts the corresponding lead angle by the phase lead circuit module; The switch circuit module comprises a triode, a current-limiting resistor and a variable resistor, wherein: The triode emitter is connected with the external power supply, and the triode base is connected with the current-limiting resistor; The variable resistor is connected with the triode collector and the phase lead circuit module, is used for changing the resistance value of the variable resistor when the triode is in conduction, and adjusting the lead angle voltage; The phase lead circuit module comprises first and second voltage dividing resistors, a voltage stabilizing diode, a filter capacitor and a phase angle processing chip, wherein: One end of the first voltage dividing resistor is connected with the external power supply, the other end of the first voltage dividing resistor is connected with one end of the second voltage dividing resistor, the other end of the second voltage dividing resistor is grounded, the voltage stabilizing diode is connected in parallel between the two ends of the second voltage dividing resistor, the filter capacitor is connected in parallel between the two ends of the voltage stabilizing diode, one end of the variable resistor is connected with the triode collector, the other end of the variable resistor is connected with one end of the second voltage dividing resistor, and the phase angle processing chip is connected in parallel between the two ends of the filter capacitor.

2. The lead-lag adaptive compensation circuit according to claim 1, wherein The phase angle processing chip comprises third and fourth voltage dividing resistors and a comparator, the third voltage dividing resistor is connected in parallel between the two ends of the filter capacitor, one end of the fourth voltage dividing resistor is connected with one end of the third voltage dividing resistor, the other end of the fourth voltage dividing resistor is connected with the input end of the comparator, the output end of the comparator is connected with the three-phase inverter circuit module, and the other end of the third voltage dividing resistor and the negative voltage pole of the comparator are grounded.

3. The lead-lag adaptive compensation circuit of claim 1, wherein, The input voltage of the external power supply is divided by the first and second voltage dividing resistors, and the output voltage is the lead angle voltage; When the voltage input value of the external power supply is greater than or equal to the first threshold value and less than or equal to the second threshold value, the motor starts and the motor winding current is at a non-rated speed, the variable resistor is adjusted to adjust the lead angle voltage when the triode conduction condition is met in the voltage interval, and the phase lead circuit module adjusts the corresponding lead angle; when the triode conduction condition is not met, the lead angle voltage value is unchanged.

4. The lead angle self-adaptive compensation circuit according to claim 3, wherein: When the voltage input value of the external power supply is greater than the second threshold value and less than or equal to the third threshold value, the motor starts and the motor winding current is at a rated speed, the variable resistor is adjusted to adjust the lead angle voltage when the triode conduction condition is met in the voltage interval, and the corresponding lead angle is adjusted.

5. The lead-lag adaptive compensation circuit of claim 1, wherein, The voltage stabilizing value of the voltage stabilizing diode is not greater than the maximum input value of the voltage of the external power supply.

6. The lead-lag adaptive compensation circuit of claim 1, wherein, The variable resistance is a negative temperature coefficient thermistor, when the temperature of the direct current motor is increased during operation and the output current waveform is distorted, the thermistor senses the temperature increase of the motor, and the resistance is correspondingly reduced.

7. The lead-lag adaptive compensation circuit of claim 1, wherein, The variable resistance is a variable resistor, when the output current waveform is distorted during operation of the direct current motor, the resistance value of the variable resistor is manually adjusted.

8. A brushless DC motor characterized by comprising: The lead angle adaptive compensation circuit comprises the lead angle adaptive compensation circuit according to any one of claims 1-7.

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